Tapered roller bearing assembly with antifriction molded cage

ABSTRACT

A tapered roller bearing cage assembly in which the retainer cage is formed of a one-piece molded plastic ring having a series of circumferentially spaced slots for receiving the roller elements of the assembly and ribs between the slots for maintaining the roller elements within the slots.

llnited States Patent 1 Harlan et al.

111 3,733,111 [451 May 15,1973

1541 TAPERED ROLLER BEARING ASSEMBLY WITH ANTIFRICTION MOLDED CAGE [75]Inventors: Jerry C. Harlan, Madison; William A. Angus, Lebanon, both ofTenn.

[73] Assignee: TRW Inc., Cleveland, Ohio [22] Filed: June 29, 1971 [21]Appl. No.: 157,931

[52] US. Cl ..308/218 [51] Int. Cl. ..Fl6c 33/46 [58] Field of Search..308/214, 217, 218

[56] References Cited UNITED STATES PATENTS Beard ..308/2l8 3,141,7117/1964 Biedinger ..308/2l8 FOREIGN PATENTS OR APPLICATIONS 775,43610/1934 France ..308/2l8 Primary ExaminerCharles .1. Myhre AssistantExaminer-Frank Susko Attorney-Carlton Hill et a1.

[57] ABSTRACT A tapered roller bearing cage assembly in which theretainer cage is formed of a one-piece molded plastic ring having aseries of circumferentially spaced slots for receiving the rollerelements of the assembly and ribs between the slots for maintaining theroller elements within the slots.

1 Claim, 6 Drawing Figures BACKGROUND OF THE INVENTION The presentinvention relates generally to the field of antifriction bearings andmore particularly to the bearing retention cages in which the rollingelements of the bearing are housed between the bearing races.

In the manufacture of antifriction (ball or roller) bearing, the rollingelements are generally fitted in a cage with either of two rings inwhich the inner and outer races are formed secured concentric to thecage. The assembly of the inner ring or the outer ring or both, alongwith the cage and rolling elements, is then either stored or shipped forfinal assembly.

In either event, means are generally required to hold the rollingelements in the cage after manufacture and until the assembly of theentire antifriction bearing is completed. Various means have beenprovided to retain the rolling elements in the cage during thisintermediate period. Generally such means have comprised an inner orouter ring which cooperates with projections which extend from a webbedsection of the cage and which are bent over the various rolling elementsafter they are inserted in the cage. Prior art rolling element retentionmeans have been generally acceptable but there are situations whichrender such cage construction and retention means less than entirelysatisfactory. First of all, there are situations (such as, for'example,in certain worm and roller manual steering gear) where the inner andouter races of the rolling elements comprise surfaces which are formeddirectly on structural components of the devices in which the bearingsare mounted. In such situations the bearing assembly, as manufacturedand shipped to the assembly point, need only comprise a retention cageand the rolling elements mounted therein. Neither an inner or outerbearing ring is required in such arrangements so far as the finalbearing assembly is concerned, although one or the other may be requiredmerely to hold the rolling elements in the cage until final assembly.

Furthermore, the cages of antifriction bearings represent an importantitem of cost in the manufacture of the overall assembly. Any reductionin cost of manufacture of cages has a significant effect in reducing themanufacturing cost of the entire assembly.

In accordance with the principles of the present invention, the rollingelements of an antifriction bearing can be easily inserted into andretained within the bearing cage without the necessity of relying uponan inner or outer ring to perform a retention function. Furthermore, thecosts involved in manufacture of the cage are reduced below thosecorresponding to cages manufactured heretofore.

In accordance with the principles of the invention, the cage comprises aone-piece injection molded plastic cage ring. While plastic cages havebeen known heretofore (see, for example, Cobb US. Pat. No. 2,550,911 andGoodwin et al. US. Pat. No. 2,550,912) the present invention utilizes anovel configuration which not only provides self-retention means for therolling elements but also offers advantages in assembly, particularly inapplications in which the inner and outer races of the bearing assemblyare formed on surfaces of structural components of the device on whichthe bearing is mounted.

In view of the foregoing, objects of the invention are to reduce themanufacturing cost of a bearing cage, to simplify the construction ofretention means for maintaining the rolling elements within the cage, toprovide a roller bearing cage with roller retention means whereby therollers may be quickly and easily inserted and retained within the cageand to provide a relatively inexpensive and easily manufactured bearingcage and rolling element assembly.

SUMMARY OF THE INVENTION In one respect, the invention may be summarizedas comprising a plastic bearing cage comprising a cage ring in which areformed a plurality of circumferentially spaced and alternately arrangedslots and ribs. The ribs are deformable from a free state to a stressedstate configuration. As the rolling elements are inserted into the cagering, the ribs are spread to permit insertion of the elements into theslots. After the rolling elements have been urged into the slots theribs resume their free state configuration, as a result of which therolling elements are retained within the slots.

While the present invention has particular utility in a variety ofapplications it is particularly suited for those applications in whichit is difficult or inconvenient or unnecessarily expensive to utilize aninner or outer ring in the bearing assembly, which ring would normallybe utilized to retain the rolling elements within the cage duringstorage, shipping and assembly of the cage and rolling elements.

The bearing cage featured in this invention is particularly advantageouswhen utilized in connection with roller bearing elements and inaccordance with the teachings of the invention may be used as a retainerfor commercial tapered roller bearing elements.

Many other features, advantages and additional objects of the presentinvention will become manifest to those versed in the art upon makingreference to the detailed description which follows and the accompanyingsheets of drawings in which preferred structural embodimentsincorporating the principles of the invention are shown by way ofillustrative example only.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially elevational andpartially sectional view of a worm and roller type steering gearassembly incorporating an antifriction bearing arrangement constructedin accordance with the principles of the present invention.

FIG. 2 is an enlarged fragmental elevational view of a bearing cage ofthe invention with tapered roller elements mounted therein.

FIGS. 3 and 4 are sectional views taken respectively along lines IlI-IIIand IVIV of FIG. 2.

FIGS. 5 and 6 are sectional views taken respectively along lines VV andVIVI of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a manuallyoperated worm and roller steering gear assembly indicated generally atreference numeral 10. The assembly 10 includes a pair of antifrictionbearing assemblies 11 and 12 constructed in accordance with theprinciples of the present invention. The bearing assemblies 11 and 12find particular utility in the steering gear assembly 10 because of therelatively low operating speed involved and because of the thrust andradial loads imposed upon the bearing assembly.

The steering gear assembly may be more particularly characterized ascomprising a housing 13 which is closed at one end by a cover 14retained on the housing 13 by means of a plurality of fastening nuts 16and lock washers 17.

The bearing assemblies 11 and 12 journal a worm 18 formed on a portionof a work input shaft 19 which extends into the housing 13. The shaft 19has a coupling portion 20 formed at the outer end thereof forintegration of the worm and roller steering gear assembly 10 in thesteering system of a dirigible vehicle.

The housing 13 has an enlarged portion forming a housing recess 21 inwhich is disposed a roller tooth subassembly indicated generally atreference numeral 22. Another cover plate 23 is retained on its adjacentportion of the housing 13 by appropriate fastening means. Referring tothe roller tooth subassembly 22, there is provided a cross shaft 24having spaced apart shaft ears indicated at 26 and 27. The ears 26 and27 extend generally parallel to one another and are disposed to projectupwardly from a lower bight portion of the cross shaft 27. A pin 28extends through bores 29 and 30 formed in the ears 26 and 27, whichbores are counter-bored at the ends thereof for receiving enlargementsformed on the opposite ends of the pin 28 for the purpose of retainingthe pin in firm assembly with the cross shaft 24.

A needle bearing assembly 31 serves to journal a roller tooth 32 on thepin 28. The roller tooth 32 is characterized as comprising a pluralityof teeth on its peripheral surface which engage mating tooth portionsformed on the worm 18.

During operation of the gear assembly 10, rotation of the work inputshaft 20 has the effect of rotating the worm 18 about the axis ofrotation of the shaft 20, which in turn rotates the cross shaft 24 aboutits axis of rotation, as will be understood by those versed in the art.The total load imposed on the worm 18 generally includes both a thrustand a radial load. These are the loads to which the bearing assemblies11 and 12 are subjected.

Since the assemblies 11 and 12 are identical only bearing assembly 12will be discussed in detail.

Referring to FIGS. 2-6 the bearing assembly 12 comprises a bearing cage33 which includes a cage ring 34 and a series of rolling elements 35which are carried on the cage ring 34. In the embodiment illustrated therolling elements 35 comprise commercial tapered roller elements, one end36 of each of which is smaller than an opposite end 37.

The cage ring 34 is similarly generally frustoconically shaped andcomprises a wall member 37, the inner and outer surfaces 38 and 39whereof constitute surfaces of revolution. Opposite ends 40 and 41 ofthe wall member 37 extend radially with respect to the axis of the cagering 34.

Provided in the wall member 37 are wall means forming a plurality ofgenerally axially extending circumferentially spaced alternatelyarranged slots 42 and ribs 43. Referring to FIG. 3, each of the slots isbounded at the axial ends thereof by means of a pair of wall or abuttingsurfaces 44 and 46 which extend in parallel relation to the end wall 36and 37 of their respective roller elements and confine or restrict theroller elements against axial movement.

In assembled relation, the axes of the roller elements 35 intersect theaxis of the cage ring 34 at a point therealong. The cage ring 34 retainsthe roller elements 35 in assembled relation until the cage assembly 33is mounted in place in the housing 13 of the device 10 or utilized insome similar application.

It is noted that the bearing assemblies 11 and 12 do not include aninner or an outer ring as are generally included in antifriction bearingassemblies. Instead, a pair of inner races 47 and 48 are formed on theends of the worm 18, and outer races 49 and 50 are formed on structuralcomponents 51 and 52 of the device 10. Since the assemblies 33 do notinclude an inner or outer race to assist in retaining the rollerelements 35 within the cage ring 34 it is highly desirable that otherretention means be provided for this purpose.

Referring again to FIGS. 2-6, the cage ring 34 is made of resilientplastic material, preferably nylon. Further, the ring 34 is of one-piececonstruction, preferably formed by means of an injection moldingprocess. That particular manufacturing process lends itself to manyeconomies in the manufacture of the ring 34, and the elastomericcharacteristics of the nylon are particularly advantageous duringassembly and retention of the roller elements 35 as discussedhereinafter.

Each of the ribs 43 comprises a pair of radially extending side walls 49and 50 connected at the radially inner ends thereof by a semi-circularwall 51. The radially outer end of each of the ribs 43 is enlarged andcomprises a pair of mutually inclined walls 52 and 53 which areconnected to the side walls 49 and 50 by means of a pair of transitionwalls 54 and 56. The facing walls 52 and 53 of adjacent ribs 51 do notextend along intersecting lines but instead extend in parallel relationto one another.

Referring to FIG. 5, it is noted that the diameter of the large end 37of each of the roller elements 35 is greater than the distance betweenthe facing walls 52 and 53 of adjacent ribs 43.

Referring to FIGS. 5 and 6, the ribs 43 extend generally radially withrespect to the axis of the cage ring 34. As a consequence, the radiallyinner ends of the ribs 43 that is, the ends adjacent the arcuate wall51, are spaced from each other circumferentially a distance which isless than the distance between the radially outer ends of the ribs 43.Thus, as shown in FIG. 6, the diameter of each of the roller elements 35at the smaller end 46 thereof is greater than the circumferentialdistance between the facing walls 50 and 49 of adjacent ribs 43.

In view of the foregoing it will be appreciated that the roller elements35 are not only restrained against axial movement in the slots 42, butare also restrained against radial movement since, at both ends 36 and37, the diameter of each of the roller elements 35 is greater than thecircumferential distance between corresponding points along the radialextent of the ribs 43.

Because of the resiliency and flexibility of the ribs 43 the rollerelements 35 are inserted into the slots 42 merely by pressing theelements 35 against the side walls of the ribs 43. After the rollerelements 35 have been inserted into the slots 43 the confining action ofthe walls of the ribs 43 serve to retain the elements 35 within theirrespective slots 42.

In this respect it is noted that both the radially inner and outer wallportions of the facing surfaces of adjacent ribs 43 arecircumferentially spaced a distance which is less than the diameter ofthe roller elements 35 at any point along the axial extent of the rollerelements 35. The central portion of the facing side walls of the ribs43, however, are circumferentially spaced a distance which is greaterthan the diameter of the roller elements 35 at a corresponding axialpoint, thus permitting limited radial movement of the roller elements 35within the slots 42.

Formed at the outer or enlarged end of the cage ring 34 is a radiallyoutwardly extending flange or bead 57 which performs the function ofaxially locating or positioning the cage 33 in the assembled conditionof the worm and roller gear assembly in one direction by abutting aradial wall 58 formed on its respective structural component 51 or 52.

It will be appreciated from the foregoing that the improved cageassembly of the present invention involves economies in manufacture,assembly, storage, transport and final assembly in the structure inwhich it is to be utilized. Thus, not only is the cage ring 34 made ofone piece injection molded plastic construction but furthermore, byvirtue of the construction and arrangement thereof, provides rollerelement retention means without the necessity of utilizing an inner orouter ring or, as is required in some prior cage assemblies, without thenecessity of bending over ears, tabs, tines or the like to retain therolling elements in the cage.

Although minor modifications might be suggested by those versed in theart, it should be understood that we wish to embody within the scope ofthe patent warranted hereon all such modifications as reasonably comewithin the scope of our contribution to the art.

What we claim is: 1. A tapered roller bearing cage assembly comprising aone-piece generally frusto-conically shaped plastic cage having meansforming thereon a series of uniform circumferentially spaced ribs forproviding roller element retention slots therebetween, and acorresponding number of roller elements held within said slots by saidribs and intersecting along the axes thereof at a point on the axis ofsaid cage,

each of said ribs comprising, in a plane normal to the axis of theadjacent roller element, a radially inner end and a radially outer endand also including a pair of generally radially extending side wallseach having a straight portion between the inner and outer ends of therib and an enlarged offset portion at the outer end thereof, thestraight portions of the two side walls of each of said ribs beingdisposed in parallel relation and the circumferential distancetherebetween constituting the greatest circumferential thickness of therib from said enlarged radially outer end to the radially inner endthereof, the circumferential distance between adjacent ribs beinggreatest between the radially inner and outer ends thereof for retentionof said roller elements therebetween.

1. A tapered roller bearing cage assembly comprising a one-piecegenerally frusto-conically shaPed plastic cage having means formingthereon a series of uniform circumferentially spaced ribs for providingroller element retention slots therebetween, and a corresponding numberof roller elements held within said slots by said ribs and intersectingalong the axes thereof at a point on the axis of said cage, each of saidribs comprising, in a plane normal to the axis of the adjacent rollerelement, a radially inner end and a radially outer end and alsoincluding a pair of generally radially extending side walls each havinga straight portion between the inner and outer ends of the rib and anenlarged offset portion at the outer end thereof, the straight portionsof the two side walls of each of said ribs being disposed in parallelrelation and the circumferential distance therebetween constituting thegreatest circumferential thickness of the rib from said enlargedradially outer end to the radially inner end thereof, thecircumferential distance between adjacent ribs being greatest betweenthe radially inner and outer ends thereof for retention of said rollerelements therebetween.